2 Drilling Pipes

Davorin Matanović

Drilling – The drill stem

The drill stem

By the definition ofAmerican Petroleum Institute (API) andInternational Association of Drilling Contractors(IADC), drill stem consists of all members in the assembly used for drilling by rotary method.

Drill collars

a) b) C)

a) standard

b) square

c) spiraled

• Drill collars are heavy, thick-walled steel pipes with threaded connections on both ends.

• On one end is the pin with external thread on the cone – male.

• On the other end is the box with internal thread –female.

Drill collars• Standard drill collars are round and about 9

meters long (drill collars up to 355,6 mm (14”) are available in lengths of up to 7,62 m).

• Spiraled drill collars are often used in small diameter holes and directional drilling to prevent differential sticking in the hole.

• Spiral groves enable mud circulation all the time.

Drill collars

• Squared drill collars are used in straight-hole drilling, and enable use of minimal clearance in packed-hole assembly.

• Contact zones are hardened with tungsten carbides of great hardness to reduce wear.

• Fluid passes around flat sides of the collar. • They help to keep the hole on course without rapid

deviations.• Available are box-pin, box-box thread connections.• Apart from standard length of 9,14 m (30 ft) , 4,57

(15 ft) and 6,1 m (20 ft) are available, too.

Drill collars according to API recommendations

BORE LENGTHBEVEL

DIAMETER(+1,6 mm;

-0 mm) (± 0,15 m) (± 0,4 mm)mm mm m mmD d L DF

NC23-31 79,4 31,8 9,1 76,2 2,57:1NC26-35 (2 3/8IF) 88,9 38,1 9,1 82,9 2,42:1NC31-41 (2 7/8IF) 104,8 50,8 9,1 100,4 2,43:1

NC35-47 120,7 50,8 9,1 114,7 2,58:1NC38-50 (3 1/2IF) 127,0 57,2 9,1 121,0 2,38:1

NC44-60 152,4 57,2 9,1 ili 9,4 144,5 2,49:1NC44-60 152,4 71,4 9,1 ili 9,4 144,5 2,84:1NC44-62 158,8 57,2 9,1 ili 9,4 149,2 2,91:1

NC46-62 (4IF) 158,8 71,4 9,1 ili 9,4 150,0 2,63:1NC46-65 (4IF) 165,1 57,2 9,1 ili 9,4 154,8 2,76:1

NC46-65 165,1 71,4 9,1 ili 9,4 154,8 3,05:1NC46-67 (4IF) 171,5 57,2 9,1 ili 9,4 159,5 3,18:1

NC50-70 (4 1/2IF) 177,8 57,2 9,1 ili 9,4 164,7 2,54:1NC50-70 (4 1/2IF) 177,8 71,4 9,1 ili 9,4 164,7 2,73:1NC50-72 (4 1/2IF) 184,2 71,4 9,1 ili 9,4 169,5 3,12:1

NC56-77 196,9 71,4 9,1 ili 9,4 185,3 2,70:1NC56-80 203,2 71,4 9,1 ili 9,4 190,1 3,02:16 5/8REG 209,6 71,4 9,1 ili 9,4 195,7 2,93:1NC61-90 228,6 71,4 9,1 ili 9,4 212,7 3,17:17 5/8REG 241,3 76,2 9,1 ili 9,4 223,8 2,81:1NC70-97 247,7 76,2 9,1 ili 9,4 232,6 2,57:1

NC70-100 254,0 76,2 9,1 ili 9,4 237,3 2,81:1NC77-110 279,4 76,2 9,1 ili 9,4 260,7 2,78:1

DRILL COLLAROUTSIDE

DIAMETER

BENDING STRENGTH

RATIO

Drill collars• Standard designation shall be stamped on the drill

collar OD with the manufacturer’s name or identifying mark, “Spec 7”, outside diameter, bore, and connection designation. (NC style connections and FH and IF sizes in parenthesis are identical if made with the V-0,038R thread form)

A 6 ¼” collar with 2 13/16” bore and NC46 connections shall be stamped:

Co (or mark)NC46-62 (4IF) 2 13/16 SPEC 7

• Drill collars with OD 209,6 i 241,3 mm have 6 5/8 REG i 7 5/8 REG connections, because there are no NC connections with adequate bending strength ratio.

• The most important is the balance of male and female connection, where bending strength of female part has to be at least 2,5 times greater than that of male part.

Mechanical properties of new steel drill collars

ELONGATION DRILL COLLAR OD

RANGE

MINIMUM YIELD

STRENGTH

MINIMUM TENSILE

STRENGTH (WITH GAUGE LENGTH

FOUR TIMES DIAMETER) mm (in) MPa MPa %

79,4 do 174,6 (3 1/2 do 6 7/8) 758 965 13 177,8 do 279,4

(7 do 11) 689 931 13

•Tensile properties shall be determined to the requirement of ASTM A-370.

•Tensile specimens shall be taken within o,9 m of the end of the drill collar, having the centerline of the tensile specimen 25 mm from the outside surface or mid wall.

•All drill collar bores shall be gauged with a drift mandrel 3,05 m (10 ft) long minimum. The drift mandrel is smaller of bore diameter for 3,2 mm (1/8”).

OD25,4 33,8 38,1 44,5 50,8 57,2 63,5 71,4 76,2 82,6 88,9 99,3 101.6(1) (1 1/4) (1 1/2) (1 3/4) (2) (2 1/4) (2 1/2) (2 4/5) (3) (3 1/4) (3 1/2) (3 3/4) (4)

73,0 (2 7/8) 28,9 26,7 23,976,1 (3) 31,8 29,6 26,9

79,4 (3 1/8) 34,8 32,6 29,982,6 (3 1/4) 38 35,8 3388,9 (3 1/2) 44,8 42,5 38,895,3 (3 3/4) 52 49,7 47 43,8101,6 (4) 59,7 57,4 54,7 51,5 47,7 43,5

104,8 (4 1/8) 63,7 61,5 58,7 55,5 51,8 47,6108,0 (4 1/4) 67,9 65,6 62,9 59,7 56,9 51,7114,3 (4 1/2) 76,7 74,3 71,6 68,4 64,6 60,4120,7 (4 3/4) 85,8 83,5 80,8 77,6 73,8 69,6 64,9

127,0 (5) 95,5 90,5 87,3 83,5 79,3 74,6133,4 (5 1/4) 105,7 100,7 97,5 93,7 89,5 84,8 78,2 73,8139,7 (5 1/2) 116,4 111,4 108,1 104,4 100,2 95,5 88,9 84,5146,1 (5 3/4) 127,5 122,6 119,3 115,6 111,4 106,7 100,1 95,7 89,5 87,3

152,4 (6) 139,2 134,3 131,0 127,3 123,1 118,3 111,7 107,4 101,2 94,5158,8 (6 1/4) 151,4 146,4 143,2 139,5 135,2 130,5 123,9 119,6 113,4 106,7 99,4165,1 (6 1/2) 164,1 159,1 155,9 152,2 147,9 143,2 136,6 132,3 126,0 119,3 112,1171,5 (6 3/4) 177,3 172,3 169,1 165,3 161,1 156,4 149,8 145,4 139,2 132,5 125,3 117,6

177,8 (7) 190,9 186,0 182,7 179,0 174,8 170,0 163,4 159,1 152,9 146,2 139,0 131,3184,2 (7 1/4) 205,1 200,1 196,9 193,2 188,9 184,2 177,6 173,3 167,1 160,4 153,1 145,4190,5 (7 1/2) 219,8 214,8 211,6 207,8 203,6 198,9 192,3 187,9 181,7 175,0 167,8 160,1196,9 (7 3/4) 234,9 230,0 226,7 223,0 218,8 214,1 207,4 203,1 196,9 190,2 183,0 175,3

203,2 (8) 250,6 245,6 242,4 238,7 234,4 229,7 223,1 218,8 212,6 205,8 198,6 190,9209,6 (8 1/4) 266,8 261,8 258,6 254,8 250,6 245,9 239,3 234,9 228,7 222,0 214,8 207,1215,9 (8 1/2) 283,4 278,4 275,2 271,5 267,3 262,5 255,9 251,6 245,4 238,7 231,5 223,8235,0 (9 1/4) 336,4 323,2 324,4 320,2 315,5 308,9 304,5 298,3 291,6 284,4 276,7241,3 (9 1/2) 355,0 346,8 343,1 338,9 334,1 327,5 323,2 317,0 310,3 303,1 295,3247,7 (9 3/4) 374,2 366,0 363,2 358,0 353,3 346,7 342,3 336,1 329,4 322,2 314,5254,0 (10) 393,8 381,9 377,6 372,9 366,3 362,0 355,8 349,0 341,8 334,1279,4 (11) 477,3 456,4 449,8 445,5 439,3 432,6 425,4 417,7304,8 (12) 568,8 547,9 541,3 537,0 530,8 524,1 516,9 509,1355,6 (14) 775,6 748,2 743,8 737,6 730,9 723,7 716,0

INNER DIAMETER, mm (in)

mm (in)

Drill collar

weights

• A string of drill collars performs several tasks: – provides weight on bit for drilling,– maintains weight to keep the drill string

from being subjected to buckling forces,– helps to provide the pendulum effect to

cause the bit to drill a more nearly vertical hole,

– stabilize the bit so that it will drill i desired direction

Weight on the bit• The amount of weight required

on the bit depends on the kind of formation being drilled, the kind of the bit, the tendency of the hole to deviate from vertical and other parameters.

• In practice it was proven that it is necessary to use such amount of drill collars to achieve that with full bit load, drill pipes remain straight.

• Usually 10 do 30% greater amount than calculated is used.

• The buoyancy effect must be considered, too.

Holding the drill pipe straight• Drill collar weight must be calculated to

include enough reserve so that the drill pipe is never subjected to buckling force.

• When drill pipe is subjected to buckling, it bends and becomes subject to increased metal fatigue failure.

• Because of the wear, the pipe body wears rapidly near the center , and tool joints wear due abrasion on the wall of the hole.

Pendulum effect

GRAVITATION

FORCE DUE PENDULUM

EFFECT

PENDULUM

STABILIZER

ONE OR MORE STABILIZER

• Pendulum effect is defined as the tendency of the pipes in string to hang in a vertical position due to gravitational force.

• Heavier pipes have greater tendency to remain vertical, and greater force is needed to decline them.

• The bit and drill collars tend to lie on the low side of the hole, all the way to the first stabilizer.

• Because of that it is desirable to have the pendulum as long as possible.

Bit stabilization• Bit stabilization secures drilling

of a vertical hole with optimal bit function, because the bit is rotating around own axis.

• That restrains bit whirling and all of cutting elements are equally weighted.

• When bit is not stabilized greater hole diameter is drilled, and hole area is not circular.

• Than the bit wears rapidly and drilling rates are smaller.

Drill collars connections

– stress relief

DISTANCE FROM CONJUNCTIVE SHOULDER

CONNECTION DIAMETER IN THREAD ROOT DRILL CILLAR

CONNECTION (tolerance +0, -3,2 mm) (tolerance +0, -0,8 mm)

Lx DRG

NC 35 85,7 82,2

NC 38 (3 1/2 IF) 92,1 89,3

NC 40 (4 FH) 104,8 96 NC 44 104,8 106,4

NC 46 (4 IF) 104,8 109,9

NC 50 (4 1/2 IF) 104,8 120,7

NC 56 117,5 134,5

NC 61 130,2 148,8

NC 70 142,9 171,1

NC 77 155,6 188,5

4 1/2 FH 92,1 106,8

5 1/2 REG 111,1 123,4

6 5/8 REG 117,5 137,7

7 5/8 REG 123,8 162,7

• Drill collar calibration is done by use of calibrating mandrel about 3 meter long with minimal diameter smaller than collar bore for 3,2 mm.

• Variations of external diameterare allowed.

• Allowed tolerances are given in table.

• Ovality is defined as the difference between minimal and maximal diameter measured on same section of the pipe and does not include any tolerances because of surface treatments.

EXTERNAL DIAMETER,

mm TOLERANCE, mm

+ - OVALITY>65,3 to 88,9 1,2 0 0,89

>88,9 to 114,3 1,6 0 1,17

>114,3 to 139,7 2,0 0 1,47

>139,7 to 165,1 3,2 0 1,78

>165,1 to 209,6 4,0 0 2,16

>209,6 to 241,3 4,8 0 2,54

>241,3 6,4 0 3,05

Surface imperfections removal

• Outer drill collar surface can differ of straightness at most0,52 mm/m of the total length.

• That means that overall difference for a drill collar of 9,1 m length can be maximal 4,74 mm.

EXTERNAL DIAMETER,

mm

MAKSIMAL HEIGHT OF REMOWED

IMPERFECTION, mm

>65,3 to 88,9 1,83 >88,9 to 114,3 2,29

>114,3 to 139,7 2,79 >139,7 to 165,1 3,18 >165,1 to 209,6 3,94 >209,6 to 241,3 5,16

>241,3 12,19

Elevator and slips recesses

• Recess fabrication reduces time needed for collar manipulation, because it excludes the need for drill collar subs or safety clamps.

• Extra attention is put on recess workup and heat treatment because of stress concentration and possible cracks.

• Use in practice had shoved greater danger of damaging (fracture).

Spiraled drill collars• Spiraled drill collar has great role

in preventing differential sticking, because when used it decrease contact area between the collar and hole wall.

• Minimal distance of recess from the box (female connection) is457,2 mm (18”), and maximal 609,6 mm (24”).

• Recess distance from the pin(male connection) is from 304,8 (12”) to 558,8 mm (22”).

• Recess fabrication lowers the weight of drill collar for about4%.

DIAMETER (mm)

RECESS (mm) NUMBER DIRRECTION

STEP (mm)

79,4-98,4 3,97±0,79 3 RIGHT 914,4±25,4101,6-111,1 4,76±0,79 3 RIGHT 914,4±25,4114,3-130,2 5,56±0,79 3 RIGHT 965,2±25,4133,4-146,1 6,35±0,79 3 RIGHT 1066,8±25,4149,2-161,9 7,14±1,59 3 RIGHT 1066,8±25,4165,1-174,6 7,94±1,59 3 RIGHT 1168,4±25,4

177,8 7,94±1,59 3 RIGHT 1652,6±25,4

Squared drill collars

• For more effective bit stabilization, squared drill collars can be used.

• In directional drilling it is usual toincorporate short squared drill collars on both ends of standard collar to enable passage through deviated part of the hole.

• When drilling in soft formations they are placed inside drill string to increase the length of rigid part of the string and preclude rapid change of hole inclination.

Lifting subs

• Drill collars without slips or elevator recess can be handled using such subs.

• Because of possible different threads on collar connections even when OD is similar, it is important to check the tread before making up connections. – New threads are made up and disengaged at

least twice with manual tongs before the use of catheads or torque wrench is allowed.

– Final torque moment must be realized with torque system that enables control of applied values.

– For drill collars with no elevator recess the use of special bushing with slips is obligatory.

– It serves to prevent the slippage of drill collars when suspended in the slips of rotary table at the time of making connections or disconnecting.

Inspection

• API RP 7G, section 10, gives recommendations for drill collar inspection.

• They first have to be visually inspected to determine obvious damage and overall condition.

• After that the ID and OD of both ends should be measured, box and pin threads cleaned and inspected for cracks by magnetic method or ultrasonic.

Inspection

• A profile gauge should be used for checking thread form and stretching.

• The box counter bore diameter is checked for swelling, and the box and pin shoulders for flatness and for damage.

• Slight damages may be repaired in the field by re facing and beveling; other must be repaired in a machine shop.

Drill pipe• Drill pipe is steel or aluminum made pipe that

serves to transmit rotation and transports the drilling fluid from the surface equipment to the bit at the bottom of the hole.

• Drill pipe outer diameter (OD) can be from 60,3 mm (2 3/8”) to 168,3 mm (6 5/8”). According to length drill pipes are divided in three groups:– class 1: from 5,49 m to 6,71 m (18 to 22 ft)

(obsolete, out of use),– class 2: from 8,23 m to 9,14 m (27 to 30 ft), – class 3: from 11,58 m to 13,72 m (38 to 45 ft).

• The most often in the use is class 2. Pipe length does not include connections that are fitted on both sides of the pipe.

Materials (steels) for drill pipe production and their properties

PROPERTIES UNIT MATERIAL GRADE D* E X95 G105 S135

MINIMAL MPa 379,2 517,1 655,0 724,0 930,8

YIELD POINT psi 55000 75000 95000 105000 135000

MAXIMAL MPa - 724,0 861,9 930,8 1137,7

YIELD POINT psi - 105000 125000 135000 165000

MINIMAL TENSILE STRENGTH MPa 655,0 689,5 758,5 792,9 999,8

psi 95000 100000 110000 115000 145000 MINIMAL ELONGATION, L=50,8 mm,

Au=483,87 mm2 % 19,5 18,5 17 16 13,5

MEDIAN MPa 448,2 586,1 758,5 827,4 999,8

YIELD STRENGTH (API RP7G) psi 65000 85000 110000 120000 145000

NOMINAL WEIGHT

NOMINAL WEIGHT

WITHOUT UPSET

WALL THICKNESS

(w) (w’) (t)inch mm kg/m kg/m mm2,375 60,30 7,22 6,60 D, E 4,83 EU

9,90 9,32 E, X, G, S 7,11 EU2,875 73,00 10,21 9,18 D 5,51 IU ili EU

15,48 14,48 E, X, G, S 9,19 IU ili EU3,5 88,90 14,14 13,12 E 6,45 IU ili EU

19,79 18,34 E, X, G, S 9,35 IU ili EU23,06 21,79 E, 11,40 IU ili EU23,06 21,79 E, X, G, S 11,40 IEU ili EU

4 101,60 17,64 15,57 E, X, G, S 6,65 IU ili EU20,83 19,26 E, X, G, S 8,38 IU ili EU

4,5 114,30 20,46 18,23 E 6,88 IU ili EU24,70 22,31 E, X, G, S 8,56 IEU ili EU29,76 27,84 E, X, G, S 10,92 IEU ili EU33,98 31,81 E, X, G, S 12,70 IEU ili EU

5 127,00 24,20 22,15 X, G, S 7,52 IU 29,02 26,71 E 9,19 IEU29,02 26,71 X, G, S 9,19 IEU ili EU38,09 35,79 E 12,70 IEU38,09 35,79 X, G, S 12,70 IEU ili EU

5,5 139,70 28,59 25,12 X, G, S 7,72 IEU ili EU32,59 29,51 E, X, G, S 9,17 IEU ili EU36,75 33,57 E, X, G, S 10,54 IEU ili EU

6,625 168,30 37,50 33,05 E, X, G, S 8,38 IEU41,25 36,06 E, X, G, S 9,19 IEU

EXTERNAL DIAMETER STEEL GRADE UPSET*(D)

Drill pipe dimensions

*EU – external upsetIU – internal upsetIEU – internal and external upset

ALLOWED DRILL PIPE STRESSES

EXTERNAL DIAMETER

NOMINAL WEIGHT ALLOWED TORQUE ALLOWED TENSION FOR MINIMUM YIELD

STRENGTH mm (inch) kg/m N⋅m daN

D E75 X95 G105 S135 D E75 X95 G105 S135 60,3 (2

3/8) 9,90 6200 8500 10700 11900 15300 45110 61510 77910 86110 110710

73,0 (2 7/8) 15,48 11500 15700 19900 21900 28200 69950 95380 120820 133540 171690 88,9 14,14 14100 19200 24300 26800 34500 63390 86450 109500 121030 155610

(3 1/2) 19,79 18400 25200 31900 35200 45300 88620 120850 153080 169180 217520 23,06 21000 28600 36200 40000 51500 105330 143640 181940 201090 258550

101,6 20,83 23200 31600 40000 44200 56800 93120 126990 160850 177780 228570 (4) 23,36 25700 35000 44300 49000 63000 105770 144230 182690 201930 259620

114,3 24,70 30600 41800 52900 58500 75200 107870 147100 186320 205940 264780 (4 1/2) 29,76 36700 50000 63400 70100 90100 134570 183500 232430 256900 330300 127,0 29,02 40900 55800 70700 78100 100500 129090 176040 222990 246450 316870

(5) 38,09 52000 70900 89800 99200 127500 173000 235920 298830 330280 424650 139,7 32,59 50400 68800 87100 96300 123800 142640 194520 246390 272320 350130 (5 1/2) 36,75 56300 76700 97200 107400 138100 162260 221260 280270 309770 398280

168,3 (6 5/8) 37,50 70200 95700 121200 134000 172300 159730 217810 275900 304940 392060

ALLOWED COLLAPSE AND BURST PRESSURES

EXTERNAL DIAMETER

NOMINAL WEIGHT

ALLOWED COLLAPSE PRESSURES FOR STEEL MINIMUM YIELD STRENGTH

ALLOWED BURST PRESSURES FOR STEEL MINIMUM YIELD STRENGTH

mm (inch) kg/m kPa kPa D E75 X95 G105 S135 D E75 X95 G105 S135

60,3 (2 3/8) 9,90 78900 107500 136200 150600 193600 78200 106700 135100 149300 192000 73,0 (2 7/8) 15,49 83500 113800 144200 159300 204900 83600 114000 144300 159500 205100

88,9 14,14 51000 69200 83100 90000 108800 - 65600 83200 92000 118200 (3 1/2) 19,79 71400 97300 123300 136200 175100 69800 95100 120500 133200 171200

23,06 84800 115600 146500 161900 208100 85100 116100 147000 162500 209000 101,6 20,83 57400 78200 99100 109600 139100 54700 74700 94600 104500 134400

(4) 23,36 65200 88900 112600 124400 160000 63000 86000 108900 120400 154700 114,3 24,70 52500 71600 87900 95300 115800 49700 67800 85800 94900 122000 (4 1/2) 29,76 65600 89300 113200 125100 160800 63400 86500 109500 121100 155700 127,0 29,02 50900 68900 82800 89600 108200 48100 65500 83000 91700 118000

(5) 38,09 68300 93100 117900 130300 167500 66300 90400 114600 126700 162800 139,7 32,59 45600 58200 68900 74000 87600 43600 59400 75200 83100 106900 (5 1/2) 36,75 52900 72100 89100 96500 117500 50100 68500 86500 95600 122900

168,3 (6 5/8) 37,50 27600 33200 36600 37800 41600 33000 45100 57100 63100 81100

JOINTS

• Joints are specialannexes to the pipe that have threads,that can be screwed-on or friction welded on the pipe body to enable pipes connecting.

• To increase pipe strength (cross section area) near the pipe end, both ends can be upset. Upset can be inside, outside or in both directions.

• External of the female joint under the welding area is furnished with 18° or 90°slope. – 18° slope conforms to often used elevators.– Male joints have shoulders with 35° slope.

Drill pipes and connections

Drill pipe and joint classification

• Every drill pipe is designed with stenciled marks.

• Company symbol month and year of welding, pipe mill code and drill pipe grade are marked on the pin’s taper.

CLASSIFICATION NUMBER AND COLOR OF STRIPES

CLASS 1 ONE WHITE

PREMIUM CLASS TWO WHITE

CLASS 2 ONE YELLOW CLASS 3 ONE BLUE

CLASS 4 ONE GREEN

SCRAP ONE RED SCRAP OR SHOP

REPAIRABLE THREE RED, APART

120º

FIELD REPAIRABLE THREE GREEN, APART 120º

(1) joint status mark

(2) pipe and joint classification mark

(3) permanent pipe body mark

THREADS• In the year 1968. API standards

have accept join designation through two digit number that conforms the dimensions of male part of joint (pin).

• That are so called numbered connections.

• Obsolete types of connections IF (internal flush – with internal upset) i FH (full hole – no upset) have been replaced with adequate types of joints according to NC classification.

• There is no proper substitution for API Regular connection, so it is still used as a bit and swivel connection.

NC CONNECTION

OLD API DESIGNATION

NC26 2 3/8 IF NC31 2 7/8 IF NC38 3 1/2 IF NC40 4 FH NC46 4 IF NC50 4 1/2 IF

MONTH AND YEAR WELDEC

Month Year

1 to 12 Last two digits of year

1 – Company Symbol ZZ (Fictional for example only) 2 – Month Welded 6 – June 3 – Year Welded 70 – 1970 4 – Pipe Mill N - United States Steel Company 5 – Drill Pipe Grade E - Grade E Drill Pipe

EXAMPLE

1 2 3 4 5

ZZ 6 70 N E

Drill pipe identification and classification

DRILL PIPE GRADE CODE PIPE MILL CODE

Grade Symbol Pipe Mill Symbol N-80 N Armco A

E E J&L Steel J

C-75 C U.S. Steel N

X-95 X Wheeling-Pittsburg P

G-105 G Youngstown Y

S-135 S Dalmine S.P.A., Italija D V-150 V Falck, Italija F

Used U TAMSA T

Nippon Kokan Kabushiki K

HEAVY WEIGHT DRILL PIPE

(Double Stencil Pipe Grade Code) Vallourec V

Mannesmannrohren-Werke M

Sumitomo Metal Ind. S

Tolerances

• Outside diameter tolerances (Table)

• Wall thickness can be up to 12,5% smaller than nominal.

• Ovality, measured on outer part of upsetmust not exceed 2,36 mm.

OUTSIDE DIAMETER TOLERANCES

101,6 mm (4”) and smaller ± 0,79 %

114,3 mm (4 1/2”) and larger ± 0,75%

•Drift test. Each length of external-upset drill pipe, except 88,9 mm (3,5”); 19,8 kg/m (13,3 lb/ft), must enable passage of a drift mandrel of 1101,6 mm length, having a diameter 4,76 mm smaller than the tabulated diameter of the drill pipe.

(1) Obsolescent thread form

(2) 0,97 mm = 0,038 in which gives the name of this thread form

(3) taper in u % = 8,33⋅taper in in/ft

(4) Thread form V 0,055 flat for small diameter connections (NC 10, NC 12, NC 13, NC 16)

API thread forms

THREAD FORM

TAPER (3) Hn hn=hs Srn=Srs i frn=frs fcn=fcs Fcn=Fcs Frn=Fr

s rrn=rrs r

% mm mm mm mm mm in mm mm mm V 0,038 R 16,66 5,49 3,09 0,97 1,43 1,65 0,065 - 0,97

(2) 0,38

V 0,038 R 25 5,47 3,08 0,97 1,42 1,65 0,065 - 0,97 0,38

V 0,040 25 4,38 2,99 0,51 0,88 1,02 0,04 - 0,51 0,38

V 0,050 25 5,47 3,74 0,63 1,09 1,27 0,05 - 0,63 0,38

V 0,050 16,66 5,49 3,75 0,63 1,1 1,27 0,05 - 0,63 0,38

V 0,055 (4) 12,5 3,7 1,4 1 1,2 1,4 0,055 1,2 - 0,38

V 0,065 (1) 16,66 5,49 2,83 1,23 1,43 1,65 0,065 1,42 - 0,38

V – 0,038 R V – 0,055

API ROTARY SHOULDERED CONNECTION

DRILL PIPE

mm (in)-(N/m) mm mm mm mm mm mm mm mm

2 3/8 REG - - - 66,7 47,6 76,2 60,1 68,3 92,1 25 52 7/8 REG 73,03 (2 7/8-IU)-151,95 95,2 31,7 76,2 54 88,9 69,6 77,8 104,8 25 53 1/2 REG 88,90 (3 1/2-IU)-194,31 107,9 38,1 88,9 65,1 95,2 82,3 90,5 111,1 25 54 1/2 REG 114,30 (4 1/2-IU)-233,76 139,7 57,1 117,5 90,5 107,9 110,9 119,1 123,8 25 54 1/2 REG 114,30 (4 1/2-IEU)-292,20 139,7 57,1 117,5 90,5 107,9 110,9 119,1 123,8 25 55 1/2 REG 139,70 (5 1/2-IEU)-319,96 171,4 69,6 140,2 110,1 120,6 132,9 141,7 136,5 25 46 5/8 REG - - - 152,2 131 127 146,2 154 142,9 16,66 47 5/8 REG - - - 177,8 144,5 133,3 170,5 180,2 149,2 25 48 5/8 REG - - - 202 167,8 136,5 194,7 204,4 152,4 25 4

3 1/2 FH 88.90 (3 1/2-IU)-194,31 117,5 61,9 101,4 77,6 95,2 94,8 102,8 111,1 25 53 1/2 FH 88,90 (3 1/2-IU)-226,46 117,5 61,9 101,4 77,6 95,2 94,8 102,8 111,1 25 5

4 FH 101,60 (4-IU)-204,54 133,3 71,4 108,7 89,7 114,3 103,4 110,3 130,2 16,66 44 1/2 FH 114,30 (4 1/2-IU)-233,76 146 76,2 121,7 96,3 101,6 115,1 123,8 117,5 25 54 1/2 FH 114,30 (4 1/2-IEU)-292,20 146 76,2 121,7 96,3 101,6 115,1 123,8 117,5 25 55 1/2 FH 139,70 (5 1/2-IEU)-319,96 177,8 101,6 148 126,8 127 142 150 142,9 16,66 45 1/2 FH 139,70 (5 1/2-IEU)-360,87 177,8 101,6 148 126,8 127 142 150 142,9 16,66 46 5/8 FH - - - 171,5 150,4 127 165,6 173,8 142,9 16,66 4

2 3/8 IF 60,33 (2 3/8-EU)-97,16 85,7 44,4 73,1 60,4 76,2 67,8 74,6 92,1 16,66 42 7/8 IF 60,33 (2 3/8-EU)-151,94 104,8 54 86,7 71,3 88,9 80,8 87,7 104,8 16,66 43 1/2 IF 88,90 (3 1/2-EU)-194,31 120,6 68,3 102 85,1 101,6 96,7 103,6 117,5 16,66 43 1/2 IF 88,90 (3 1/2-EU)-226,46 127 68,3 102 85,1 101,6 96,7 103,6 117,5 16,66 4

4 IF 101,60 (4-EU)-204,54 146 82,5 122,8 103,7 114,3 117,5 124,6 130,2 16,66 44 1/2 IF 114,30 (4 1/2-EU)-233,76 155,6 95,2 133,3 114,3 114,3 128,1 134,9 130,2 16,66 44 1/2 IF 114,30 (4 1/2-EU)-233,76 158,7 95,2 133,3 114,3 114,3 128,1 134,9 130,2 16,66 44 1/2 IF 127,0 (5-IEU)-284,90 161,9 95,2 133,3 114,3 114,3 128,1 134,9 130,2 16,66 44 1/2 IF 127,0 (5-IEU)-284,90 165,1 88,9 133,3 114,3 114,3 128,1 134,9 130,2 16,66 45 1/2 IF - - - 162,5 141,3 127 157,2 163,9 142,9 16,66 4

V-0,065V-0,065V-0,065V-0,065

V-0,065V-0,065V-0,065V-0,065

V-0050INTERNAL FLUSH (IF) (4)

V-0065V-0065

V-0040V-0040V-0050V-0050

FULL HOLE (FH) (4)V-0040V-0040V-0065

V-0050V-0050V-0050V-0050

V-0,040V-0,040V-0,040V-0,040

REGULAR (REG)V-0,040

TAPER %

THREADS PER 25,4

mm

THREAD FORM

CONNECTION NUMBER AND SIZE

Df Lf

TOOL JOINT PIN BOXDIAMETER - UPSET

WEIGHTOUTSIDE

DIA.INSIDE DIA. Dm dm Lm Dc

(1) The number(NC) is the pitch diameter of the pinthread at the gage point rounded to units and tenths of inch.

(2) Connections in the NC style are interchangeable with FH i IF connections, if they have the same pitch diameter.

•Interchangeable are: NC 26 and 2 3/8 IF, NC 31 and 2 7/8 IF, NC 38 and 3 1/2 IF, NC 40 and 4 FH, NC 46 and 4 IF, NC 50 and 4 1/2 IF

• NC 10, 12, 13, 16 and 23 are tentative for small diameter work strings. For high pressure use an “O” ring is optional at the base of the pin shoulder.

(3) It is recommended to use grease with 40 do 60% of zinc powder by weight.

(4) Interchangeableare NC 50 (4 1/2 IF) tool joint with 6 3/8”and 6 1/2”outside diameter, it is used on 5” IU drill pipes named 5”Extra-Hole and5” Semi-Internal-Flush

Drill pipe connections (continued)DRILL PIPE

mm (in)-(N/m) mm mm mm mm mm mm mm mm

NC 10 26,67 (1,050)-22,65 34,9 18,3 30,2 25,5 38,1 27 30,6 54 12,5 6 V-0,055NC 12 33,40 (1,315)-33,60 41,3 23 35,4 29,8 44,4 32,1 35,7 60,3 12,5 6 V-0,055NC 13 42,16 (1,660)-46,07 46 23,8 38,6 33 44,4 35,3 38,9 60,3 12,5 6 V-0,055NC 16 48,26 (1,900)-61,22 54 25,4 44,1 38,5 44,4 40,9 44,5 60,3 12,5 6 V-0,055NC 23 - - - 65,1 52,4 76,2 59,8 66,7 92,1 16,66 4 V-0,038RNC 26 60,33 (2 3/8-EU)-97,16 85,7 44,4 73,1 60,4 76,2 67,8 74,6 92,1 16,66 4 V-0,038RNC 31 73,03 (2 7/8-EU)-151,94 104,8 54 86,1 71,3 88,9 80,8 87,7 105 16,66 4 V-0,038RNC 35 - - - 95 79,1 95,2 89,7 96,8 111 16,66 4 V-0,038RNC 38 88,90 (3 1/2-EU)-194,31 120,6 68,3 102 85,1 102 96,7 104 118 16,66 4 V-0,038RNC 38 88,90 (3 1/2-EU)-226,46 127 65,1 102 85,1 102 96,7 104 118 16,66 4 V-0,038RNC 40 101,60 (4-IU)-204,54 133,3 71,4 109 89,7 114 103 110 130 16,66 4 V-0,038RNC 40 101,60 (4-IU)-204.54 139,7 71,4 109 89,7 114 103 110 130 16,66 4 V-0,038RNC 44 - - - 118 98,4 114 112 119 130 16,66 4 V-0,038RNC 46 101,60 (4-EU)-204,54 146 82,5 123 104 114 118 125 130 16,66 4 V-0,038RNC 46 114,30 (4 1/2-IU)-233,76 152,4 82,5 123 104 114 118 125 130 16,66 4 V-0,038RNC 46 114,30 (4 1/2-IU)-233,76 158,7 82,5 123 104 114 118 125 130 16,66 4 V-0,038RNC 46 114,30 (4 1/2-IEU)-292,21 152,4 76,2 123 104 114 118 125 130 16,66 4 V-0,038RNC 46 114,30 (4 1/2-IEU)292,21- 158,7 76,2 123 104 114 118 125 130 16,66 4 V-0,038RNC 50 114,30 (4 1/2-EU)-233,76 155,6 95,2 133 114 114 128 135 130 16,66 4 V-0,038RNC 50 114,30 (4 1/2-EU)-233,76 158,7 95,2 133 114 114 128 135 130 16,66 4 V-0,038RNC 50 127,00 (5-IEU)-284,90 161,9 95,2 133 114 114 128 135 130 16,66 4 V-0,038RNC 50 127,00 (5-IEU)-284,90 165,1 88,9 133 114 114 128 135 130 16,66 4 V-0,038RNC 56 127,00 (5 1/2-IEU)-319,96 177,8 95,2 149 118 127 142 151 143 25 4 V-0,038RNC 61 - - - 164 129 140 157 165 156 25 4 V-0,038RNC 70 - - - 186 148 152 179 187 168 25 4 V-0,038RNC 77 - - - 203 162 165 197 205 181 25 4 V-0,038R

dm Lm DcDIAMETER - UPSED WEIGHT

OUTSIDE DIA.

INSIDE DIA. Dm

NC tip (1) (2)

CONNECTION

NUMBER AND SIZE

TAPER %

THREADS PER 25,4

mm

THREAD FORMDf Lf

TOOL JOINT PIN BOX

Upset drill pipes for weld-on tool joints

Heavy-wall drill pipes 3 1/2"

(26 lb/ft) 4"

(28 lb/ft) 4 1/2" (42 lb/ft)

5" (50 lb/ft)

4 1/2" (42 lb/ft)

5" (50 lb/ft)

88,9 mm (38,68 kg/m)

101,6 mm (41,66 kg/m)

114,3 mm (62,49 kg/m)

127 mm (74,39 kg/m)

114,3 mm (62,49 kg/m)

127 mm (74,39 kg/m)

II II II II III IIIEXTERNAL DIAMETER mm 52,4 65,1 69,8 76,2 69,8 76,2

WALL THICKNESS mm 18,2 18,2 22,2 25,4 22,2 25,4CROSS SECTION AREA mm2 4051 4779 6427 8106 6427 8106

END UPSETS mm 92,1 104,8 117,5 130,2 117,5 130,2CENTRAL UPSET

mm 101,6 114,3 127,0 139,7 127,0 139,7NC38

(3 1/2IF)NC40 (4FH)

NC46 (4IF)

NC50 (4 1/2IF)

NC46 (4IF)

NC50 (4 1/2IF)

EXTERNAL DIAMETER mm 120,6 133,3 158,7 165,1 158,7 165,1INSIDE DIAMETER mm 55,6 68,3 73,0 77,8 73,0 77,8

kg/m 37,7 44,2 61,0 73,5 59,4 72,2

dm3/m 2,19 3,37 3,87 4,61 3,87 4,61

dm3/m 4,81 5,64 7,79 9,36 7,57 9,2

dm3/m 7,00 9,01 11,66 13,97 11,44 13,81PIPE

103 N1535 1815 2438 3074 2438 3074

JOINT103 N

3332 3163 4564 5631 4564 5631

PIPEN·m

26540 37468 55202 76537 55202 76597

JOINTN·m

23828 31896 52605 69655 52605 69655

N·m 13423 17964 29557 39851 29557 39851MAKE-UP TORQUE

NOMINAL DIAMETER

(MASS PER UNIT LENGTH)

PIPE AND JOINT MASS

INTERIOR VOLUME

STEEL VOLUME

EXTERIOR VOLUME

CLASSPI

PE B

OD

Y

TYPE

JOIN

TTE

NSI

LE

STR

ENG

THTO

RSI

ON

AL

YIEL

D

Are intermediate drill string member

Heavy-wall drill pipes

• They were originally developed for three reasons:– As a transition member to be run between

drill pipe and drill collars.– As a flexible weight member to be run in

directional drilling.– And as a weight member on small rigs,

drilling small diameter holes.

Protectors• Help prevent damage to

the tool joint. • Are produced as pressed

steel, cast steel, plastic or rubber parts.

• Can be with threads, or can be stabbed (rubber).

• Thread protector is a device that is screwed into the box or onto the pin of a tool joint to keep the threads and shoulders from being damaged while pipe is moved or stored.

Cleaning• Pin and box threads and shoulders of tool

joints should be always thoroughly cleaned before added to the drill string.

• The intention is to remove foreign materials, to permit proper makeup.

• Then better inspection of thread and shoulder is possible.

• By eliminating abrasive materials the life of connections is increased.

• Cleaned and lubricated joints are protected with protectors.

Lubrication• Lubricant in thread serves

to transport loads from one side of thread to another because of tolerances between threads (box/pin) .

• Regular lubricants recommended by IADC and API contain metallic fillers up to 40 or 60% (zinc powder) so they are not squeezed easily from the thread.

Failure• If joint wobbles, that means there

is some movement between surfaces of the mating box and pin. – Work with the joint that is wobbling

results with failure. – To high or to small makeup torque can

cause the joint to wobble. The cause is improper tong position, neglecting the angle between the tong lever and dragging line.

– Than proper make up torque is not achieved.

– Result is additional makeup during bit rotation, and box swelling by overtorque (picture).

Makeup torque

– To high or to small makeup torque can cause the joint to wobble.

– The cause is improper tong position, neglecting the angle between the tong lever and dragging line.

• The earliest indication of wobble is a dry or muddy appearance of pins.

• This shows that tool joint is not pressure-tight, and lubricant is displaced by drilling fluid.

• Close examination of connections helps to reveal any damage.

• If wobble causes shoulder damage it must be repaired in field or joint must be removed.

• Fouled and broken threads can not form an effective seal against leakage.

• Damage due to pipe manipulation must be avoided.

• The most common damage is on pin thread and shoulder.

• Damage also results with flattened threads because of improper handling.

• Pin cracks at the root of the thread.

• Thread identification by the use of joint identifier helps to connect proper joints, and avoid failures.

Transport and Storage• All pipes have to be stored with the box faced to

the rig side of the rack. – All threads should be covered with protectors. – To ensure good ventilation, first tier of pipes on rack

should be at least 0,3 m from the ground. – Maximal height of pipes stored on rack is 3 m, and in

the derrick finger maximal five layers are allowed .

Kelly• The kelly is the heavy

square, hexagonal, or triangular steel pipe that is used with rotary table drive bushing to transmit rotation through drill string to the bit.

• At the same time it allows the mud passage through.

Squared kelly data

mm (in) THREAD (RIGHT) mm

stand. opt. stand. opt. stand. opt. stand. opt. stand. opt.

LD LD L L DFL Dc Rc Du Du Lu DF DF DL LL DF d63,5

(2 1/2) 11,3 12,2 63,5 83,3 7,9 6 5/8 Reg 4 1/2 Reg 196,9 146,1 406,4 186,1 134,5 NC 26 (2 3/8 IF) 85,7 508 82,9 31,876,2 (3)

11,3 12,2 76,2 100 9,5 6 5/8 Reg 4 1/2 Reg 196,9 146,1 406,4 186,1 134,5 NC 31 (2 7/8 IF) 104,8 508 100,4 44,588,9

(3 1/2) 11,3 12,2 88,9 115,1 12,7 6 5/8 Reg 4 1/2 Reg 196,9 146,1 406,4 186,1 134,5 NC 38 (3 1/2 IF) 120,7 508 116,3 57,2

NC 46 (4 IF) 152,4 508 145,3 71,4

NC 50 (4 1/2 IF) 155,6 508 150,4 69,9

5 1/2 FH 177,8 508 171,1 82,6

NC 56 177,8 508 170,7 82,6

133,4

16,5

16,5

LOW

ER

SEC

TIO

N

OVE

RAL

L LE

NG

TH

DR

IVE

SEC

TIO

N

UPP

ER

SEC

TIO

N

114,3

175,4

12,7

EXTE

RN

AL

DIA

MET

ER

DR

IVE

SEC

TIO

N

LEN

GTH

108

INS

IDE

DIA

MET

ER

mm mm THREAD (LEFT) mm mm

15,9

6 5/8 Reg

6 5/8 Reg

4 1/2 Reg 196,9

196,9

146,1

146,1

406,4

406,4

186,1

186,1

134,5108,0

(4 1/4)133,4

(5 1/4)

11,3

11,3

15,5

15,5

12,2

12,2

Hexagonal kelly data

mm (in) THREAD (RIGHT) mm

stand. opt. stand. opt. stand. opt. stand. opt. stand. opt.

LD LD L L DFL Dc Rc Du Du Lu DF DF DL LL DF d76,2 (3)

11,3 12,2 76,2 85,7 6,4 6 5/8 Reg 4 1/2 Reg 196,9 146,1 406,4 186,1 134,5 NC 26 (2 3/8 IF) 85,7 508 82,9 38,188,9

(3 1/2) 11,3 12,2 88,9 100,8 6,4 6 5/8 Reg 4 1/2 Reg 196,9 146,1 406,4 186,1 134,5 NC 31 (2 7/8 IF) 104,8 508 100,4 44,5108,0 (4 1/4) 11,3 15,5 12,2 16,5 108 122,2 7,9 6 5/8 Reg 4 1/2 Reg 196,9 146,1 406,4 186,1 134,5 NC 38 (3 1/2 IF) 120,7 508 116,3 57,2

NC 46 (4 IF) 152,4 508 145,3 76,2

NC 50 (4 1/2 IF) 155,6 508 150,5 82,6

5 1/2 FH 177,8 508 170,7 88,9

NC 56 177,8 508 171,1 88,9

133,4

(5 1/4)152,4

(6)

196,9 406,4 186,111,3 15,5 12,2 16,5 152,4 159 9,5 6 5/8 Reg

196,9 406,4 186,1151,6 9,5 6 5/8 Reg15,5 12,2 16,5 133,411,3

UP

PE

R

SE

CTI

ON

LOW

ER

S

EC

TIO

N

INS

IDE

D

IAM

ETE

R

m m mm THREAD (LEFT) mm mm

EXT

ER

NA

L D

IAM

ETE

R

DR

IVE

S

EC

TIO

N

LEN

GTH

OV

ER

ALL

LE

NG

TH

DR

IVE

S

EC

TIO

N

Kelly properties

mm (in) mm mm mm daN daN kN·m kN·m kN·m kN·m

63,5 squared (2 1/2) 31,8 NC 26 (2 1/2 IF) 85,7 114,3 185000 242000 13 21 20 30

76,2 squared (3) 44,5 NC 31(2 7/8 IF) 104,8 139,7 238000 317000 19 33 33 49

88,9 squared (3 1/2) 57,2 NC 38 (3 1/2 IF) 120,7 168,3 322000 394000 31 48 49 75

108 squared (4 1/4) 71,4 NC 46 (4 IF) 152,4 219,1 469000 683000 63 83 85 132

108 squared (4 1/4) 69,9 NC 50 (4 1/2 iF) 155,6 219,1 632000 569000 78 85 87 134

133,4 squared (5 1/4) 82,5 6 1/2 FH 177,8 244,5 716000 925000 99 168 170 258

76,2 hexagonal (3) 38,1 NC 25 (2 3/8 IF) 85,7 114,3 159000 294000 11 34 35 31

88,9 hexagonal (3 1/2) 47,5 NC 31 (2 7/8 IF) 104,8 139,7 220000 385000 18 52 55 47

108 hexagonal (4 1/4) 57,2 NC 38 (3 1/2 IF) 120,7 168,3 322000 569000 31 94 101 85

133,4 hexagonal (5 1/4) 76,2 NC 46 (4 IF) 152,4 219,1 427000 820000 48 169 183 164

133,4 hexagonal (5 1/4) 82,5 NC 60 (4 1/2 IF) 155,6 219,1 517000 750000 63 159 174 145

152,4 hexagonal (6) 88,9 5 1/2 FH 177,8 244,6 651000 1052000 90 249 270 227

DIAMETER AND TYPE INSIDE DIA. LOWER THREAD

TYPE AND DIA. EXTERNAL

DIA.

MINIMAL INSIDE

CASING DIA.

ALLOWED BENDING

MOMENTDRIVE SECT.

DIAG.

DRIVE SECT. FLATS

ALLOWED TENSILE

FORCEUPPER

CONNEC.

DRIVE

SECT.

ALLOED TORQUE

LOWER

CONNEC.

DRIVE

SECT.

• all values are determined without safety factor based on minimal tensile strength of 758 MPa and torsionalstrength of 57,7% minimal tensile strength

• tensile force is calculated for the area in the thread root19,1 mm from connection shoulder

Drill Stem Auxiliaries

• With drill stem, various auxiliaries are used: drill stem subs, stabilizers, lifting subs, vibration dampeners, reamers, pipe wipers, protectors, etc.

• Subs or substitutes, are short thread pieces of pipes used to connect parts of the drilling assembly for various reasons.

KELLY SUB

CROSSOVER SUB

DRILL COLLAR SUB

BIT SUB

Pipe wipers

• Pipe wipers are rubber rings that fits around the pipe and clean mud off as the pipe comes out of hole.

• It also keeps junk from falling in-to the hole during tripping.

Pipe protectors

• Pipe protectors are used on drill pipe to protect tool joints from rubbing against the casing or the wall of the hole

Stabilizers and reamers• Stabilizers are used in

the assembly of drill collars to stabilize bit and the drill collars in the hole, or to help to maintain in the desired direction.

• They can be divided in two groups:– Stabilizers with stationary

blades and – stabilizers with rotating

blades

Welded blades

• Stabilizers with integrated blades are especially durable, and are used in hard and abrasive formations.

• The ribs are milled directly on body, that prevents loss of ribs in hole.

• Ribs can be straight or spiral and are had faced with granular Tungsten Carbide.

• Stabilizers with replaceable sleeve are of the integral type stabilizers but with two parts; body and the sleeve. – Sleeve is preheated to the

340 °C (750 °F), and latched on the body, and then cooled.

– Ribs are hard faced with granular Tungsten Carbide or pressed inserts.

– Same body can be used several times, and the sleeve is changed.

• Stabilizers with screwed sleeve can be used in hardest formations. – They consist of

exchangeable sleeve with ribs that is screwed on the body.

– Body can be used several times during the process by changing the sleeve, of different shapes and external diameters.

• Stabilizers with replaceable wear pad (ribs) are often usedabove the bit when maintaining the clearance is of crucial importance; especially in hard formations.

• Stabilizers with non-rotating sleeve have metal body and rubber sleeve stabilizer. – While drilling the rubber sleeve

stands still and drill pipes and the stabilizer body are rotating.

– That saves the sleeve of excessive wear, and the influence on the hole wall is minimal.

– Constraint in use are small ability to maintain hole diameter, and possible use below 120 °C (250 °F).

– Endurance is greatly influenced by the rock hardness and abrasiveness.

• The body is produced so that the ribs are inserted and fixed with screws and nuts.

Reamers with cylindrical cutters

• Roller reamers are run between the bit and drill collars to maintain hole gauge in hard formations, when rocks are susceptible to swelling or the bit wears very fast according to caliper.

• It is also used for additional stabilization in hard formations, bat the role is small because of little contact area with hole walls.

Vibration dampeners• A vibration dampener works as a shock

absorber; it permits normal drilling and saves drill string from damaging bounce and vibration due the work of roller cone bits.

• Dampening is achieved by the use of rubber, springs, compressed gas, or other spring elements for absorbing shock.

• Optimal position for dampener is directly above the bit.

• With packed-hole stabilization, the ideal location is 3 meter from the bit, with additional stabilization about 9 meters upwards, to prevent excessive lateral loading.

• Axial stressDrill pipe stresses

sav A

F=σ (axial)

( ) ddDF σπ⋅−⋅= 22

4σav - axial stress due the tensile force, Pa

F – tensile force, N

As –pipe cross section area, m2.

π – Ludolf’s number (3,14)

σd – yield point, Pa

• Allowed tensile force on joint depends on type of connection; welded or screwed. When screwed the height of the thread on both sides along diameter must be considered.

• Calculations are done according to the area on the thread base near the thread root.

( )[ ]2224

dhDF sdsp −⋅−⋅⋅=πσ

Fsp – allowed axial force in the connection, N

hs – thread height, m

• When pipe is under compression (F has negative sign), the pipe bends.

⎥⎦

⎤⎢⎣

⎡⋅⋅

+⋅=IrR

AF o

sat 2

1σ

σat – axial stress due the axial compressive force, Pa

R – radial clearance, m (R=(dz-D)/2)

ro – outer pipe radii, m

I – cross section moment of inertia, m4

(I=π/64·(D4-d4))

dz – inner diameter of casing or the hole, m

(compressive)

Example 1.

• Determine allowed tensile force for drill pipes of external diameter D=0,1143 m, inside diameter d=0,09718 m and materialG-105 (105000 psi).

• Yield point defined for SI system of units is:

Pa6107246895105000 ⋅=⋅=dσ

• Pipe cross section are is:

• Allowed tensile force is:

( ) ( )2

2222

028386,0

09718,01143,0414,3

4m

dDAs

=

=−⋅=−⋅=π

N 4,2055117028386,010724 6 =⋅⋅=⋅= sd AF σ

Stresses due torsion• Greatest stress due

the torsion is generated at the perimeter of the pipe and is presented with following equation:

• Allowed cross section stress due the torsion is:

τd – allowed pipe stress due torsion, Pa

( )44

16dDDMt

t −⋅⋅⋅

=π

τ

τt – stress due the torsion, Pa

Mt – torque moment, N·m

dd στ 75,0≤

Burst• Burst can be the result

of inside pressure (pi) effects on pipe wall area. Burst pressure is determined form the equation:

pi(r) – burst pressure, Pat – pipe wall thickness, mDn – nominal pipe

diameter, m

• For proper determination of this pressure it is recommended to use Barlow’s equation for thick wall pipes. Because of allowed difference in wall thickness from nominal to minimal, the value of87,5% is planed in Barlow’s equation. The API burst-pressure rating is based on this equation:

Dt

p dri

⋅⋅=

σ2)(

n

dri D

tp

⋅⋅⋅=

σ2875,0)(

Example 2. • Determine burst pressure of drill pipes

with outside diameter D=0,1143 m, inside diameter d=0,09718 m wrought from material G-105.

• Solution:

Pa

Dt

pn

dri

56

)(

1086,9481143,0

00856,0107242875,0

2875,0

⋅=⋅⋅⋅

⋅=

=⋅⋅

⋅=σ

Collapse• Collapse pressure rating is the

minimum external pressure that will cause the coiled tubing walls to collapse in the absence of internal pressure and axial loading.

• The radial and hoop stresses can be calculated using Lame’s equations:

( ) ( )( )222

222222

io

ioooiir rrr

rrrprrrp−⋅

−⋅⋅−−⋅⋅−=σ

( ) ( )( )222

222222

io

ioooiit rrr

rrrprrrp−⋅

+⋅⋅−+⋅⋅=σ

σr – radial stress, Pa

σt – tangential stress, Pa

ri – inner pipe radii, m

ro – external pipe radii, m

r – pipe medium radii, m

po – external pressure, Pa

pi – internal pressure, Pa

• Elastic collapse; as the moment of inertia of the tube increases (or equivalently, the length decreases) or as the diameter of cross section decreases (or thickness increases), the point will be reached where buckling does not occur until the axial or hoop stress exceeds the material’s yield strength. That happens only for small (Dn/t)ratios, with lower value.

( ) ( ) ( )

( ) ⎥⎦⎤

⎢⎣

⎡+⋅

−+⎥⎦

⎤⎢⎣

⎡+⋅+−

≤

ed

CB

Aed

CBA

n

FF

FFFF

tD

σ

σ

2

282 2

• Effective strength (σd)e, is equal to yield strength (σd), when axial stress equals zero.

• Allowed collapse pressure is than (pcr):

MATERIAL QUALITY FA FB FC (106 Pa) FD FE

H-40 2,95 0,0465 5,2 2,063 0,0325-50 2,976 0,0515 7,28 2,003 0,0347

J-55, K-55 2,991 0,0541 8,32 1,989 0,036-60 3,005 0,0566 9,35 1,983 0,0373-70 3,037 0,0617 11,42 1,984 0,0403

C-75 3,054 0,0642 12,45 1,99 0,0418L-80, N-80 3,071 0,0667 13,48 1,998 0,0434

C-90 3,106 0,0718 15,54 2,017 0,0466C-95 3,124 0,0743 16,58 2,029 0,0482-100 3,143 0,0768 17,6 2,04 0,0499

P-105 3,162 0,0794 18,63 2,053 0,0515P-110 3,181 0,0819 19,66 2,066 0,0532-120 3,219 0,087 21,73 2,092 0,0565-125 3,239 0,0895 22,76 2,106 0,0582-130 3,258 0,092 23,79 2,119 0,0599-135 3,278 0,0946 24,83 2,133 0,0615-140 3,297 0,0971 25,86 2,146 0,0632-150 3,336 0,1021 27,95 2,174 0,0666-155 3,356 0,1047 28,99 2,188 0,0683-160 3,375 0,1072 30,03 2,202 0,07-170 3,412 0,1123 32,13 2,231 0,0734-180 3,449 0,1173 34,24 2,261 0,0769

EMPIRICAL COEFFICIENT

( )

⎥⎥⎥⎥⎥

⎦

⎤

⎢⎢⎢⎢⎢

⎣

⎡

⎟⎟⎠

⎞⎜⎜⎝

⎛

−⋅⋅= 2

12

tDt

D

pn

n

edcr σ

pcr – critical collapse pressure, Pa

(σd)e – effective yield strength, Pa

• Upper value of (Dn/t) ratio for collapse in yield deformation area is determined from, and than plastic collapse exists:

( ) ( )( ) ( )

( ) ( ) ( )

( ) ⎥⎦⎤

⎢⎣

⎡+⋅

−+⎥⎦

⎤⎢⎣

⎡+⋅+−

≥≥−⋅+

−⋅

ed

CB

Aed

CBA

n

EBedC

DAed

FF

FFFF

tD

FFFFF

σ

σ

σσ

2

282 2

• Area of plastic deformations is determined by (Dn/t) values right under such that are valued for yield collapse, and collapse pressure is than determined as:

( ) CBn

Aedcr FF

tDF

p −

⎟⎟⎟⎟

⎠

⎞

⎜⎜⎜⎜

⎝

⎛

−⋅= σ

• Transition region is that among plastic and yield area, and collapse is there determined as:

( )⎟⎟⎟⎟

⎠

⎞

⎜⎜⎜⎜

⎝

⎛

−⋅= En

Dedcr F

tDF

p σ

( ) ( )( ) ( )EBedC

DAedn

A

B

A

B

FFFFF

tD

FFFF

−⋅+−⋅

≥≥⋅

+

σσ

3

2

• For high (Dn/t) ratios collapse is defined with modified Clindendinst equation:

( )2

11

22 1

1022488,3

11

275,095,0

⎟⎠⎞

⎜⎝⎛ −⋅⎟

⎠⎞

⎜⎝⎛

⋅=

⎟⎠⎞

⎜⎝⎛ −⋅⎟

⎠⎞

⎜⎝⎛⋅−

⋅⋅⋅=

tD

tD

tD

tD

Epnnnn

cr

ν

A

B

A

B

n

FFFF

tD

⋅

+≥ 3

2

MATERIALQUALITY

H-40-50

J-55, K-55-60-70

C-75L-80, N-80

C-90C-95-100

P-105P-110-120-125-130-135-140-150-155-160-170-180 11,23 17,47 19,93

11,52 18,19 21,3211,37 17,82 20,6

11,67 18,57 22,1111,59 18,37 21,7

11,92 19,18 23,4411,84 18,97 22,98

12,11 19,63 24,4612,02 19,4 23,94

12,44 20,41 26,2212,21 19,88 25,01

12,7 21 27,612,57 20,7 26,89

13,01 21,69 29,1812,85 21,33 28,36

13,6 22,91 32,0513,38 22,47 31,02

14,44 24,42 35,7313,85 23,38 33,17

15,24 25,36 38,8314,81 25,01 37,21

ELASTIC

→

16,4 27,01 42,64

YIELD POINT

PLASTIC

→ ←

TRANSITION

→ ←

(Dn/t) ratios for various areas of collapse pressure when axial stress

equals zero

• Determine allowed collapse pressure for casing with nominal diameter; Dn=244,48 mm (9 5/8”), material P-110 (σd=758,45⋅106 Pa), with nominal wall thickness; t=13,84 mm.

• (Dn/t) ratio of chosen pipe is:

Example3.

• Critical collapse pressure is than determined from:

66,1701384,024448,0

==t

Dn

( )

Pa

FF

tDF

p CBn

Aedcr

566 102,5481066,190819,0

01384,024448,0181,31045,758 ⋅=⋅−

⎟⎟⎟⎟

⎠

⎞

⎜⎜⎜⎜

⎝

⎛

−⋅⋅=

=−

⎟⎟⎟⎟

⎠

⎞

⎜⎜⎜⎜

⎝

⎛

−⋅= σ